Drones Deliver a Fresh Take on Airborne Imaging Applications

HANK HOGAN, CONTRIBUTING EDITOR

Initially swooping in to provide aerial shots in big-budget movies, unmanned aerial vehicles (UAVs) — or drones, in consumer parlance — are now bringing aerial cinematography technology to other applications. Drone-mounted imagers are helping to inspect infrastructure, monitor crops, and conduct search and rescue operations. They could eventually deliver vital goods. As demand grows for these high-flying imaging platforms, the technology is evolving to allow drones to perform finer maneuvers, capture higher-quality images, and stay airborne longer.

Two drones fly over a railroad bridge to capture aerial cinematography images. Drone-mounted cameras produce aerial images that cannot easily be created by any other means, including other aircraft. Courtesy of Freefly Systems.

Once reliant on helicopters and airplanes, aerial cinematography became more practical as filmmakers began to mount high-end cameras on custom-built drones with the goal of cutting costs. But the real value of this innovation has only begun to emerge as end users in other fields contemplate the potential roles that drone-based imaging technology could play.

Elevating performance

“What are the shots that you can only do using a drone?” asked Tabb Firchau while speculating about the drone’s use and expanding application. Firchau — who is president of Freefly Systems, a manufacturer of camera movement systems that are used extensively in cinematography — said that, years ago, shots from drones did not share the same quality as those from helicopters. At the time, drones were single-rotor affairs, making them unstable and mechanically complicated. The advent of multirotor drones fixed many of these early problems, but other innovations such as inertial measurement units (IMUs) also helped. IMUs leverage accelerometers, gyroscopes, and other tools to sense a drone’s movement, pitch, and orientation to determine its position and aid in navigation. The devices can also help counter small movements that affect image quality. Further improvements came from better cameras and optics, which also became smaller, lighter, and more robust.

Current U.S. aviation regulations require drones to operate within the line of sight of a pilot on the ground. Combined with battery-related range constraints, this limits how far drone-mounted cameras can operate. But regulations and technical limits are subject to change, and autonomous drones offer clear benefits. Courtesy of Freefly Systems.

The result is that drones today are more stable and, under current regulations, can smoothly capture images while flying at speeds up to 100 mph and to heights reaching 400 ft — or higher if the craft remains within 400 ft of a structure.

Firchau recalled a car commercial from a quarter century ago for which flying helicopters were used to get an aerial shot. At the time, it was considered a success to simply get the car in the camera frame. Today, drone pilots can ensure the driver’s head appears in the frame and make minute adjustments to create a better and more compelling visual experience.

“Drones can fly really intimate and dynamic scenes, but we’re typically limited either by practicality or regulation to a location that’s fairly close to the takeoff site,” Firchau said.

In the future, he said, aerial cinematography could benefit from lighter-weight lenses with longer focal lengths. Extending the focal length would help to capture more dramatic images by allowing background objects to fill the frame more fully. Other desired advancements would involve more compact, higher-resolution, and lighter cameras.

Lightening the load

Today’s technology has already proven its worth in many films, including Marvel Studios’ 2015 “Avengers: Age of Ultron.” Building on these successes, companies beyond the film industry are now using drone-based images for other applications.

One such company is Rocky Mountain Unmanned Systems LLC (RMUS). Based in Salt Lake City, it offers drone-enabled high-resolution mapping services. The sensor packages on its drones often include a visible-range camera, an infrared sensor, lidar, and sometimes ground penetrating radar. Yet the entire payload fits within strict weight limits, said Ryan Wood, vice president of sales and marketing at RMUS. For regulatory reasons, fully loaded commercial drones typically cannot weigh more than 55 lbs, which puts pressure on suppliers designing sensors and optics for these applications.

“Every ounce, every gram counts,” said Wood, who added another reason for cutting sensor weight: “Maximizing your flight time is important.”

Minimizing the weight of the sensor package reduces power consumption and frees some of the weight budget for more power storage capacity in the battery, which can translate to longer flight times.

Today, an industrial-grade drone equipped with a multimegapixel-resolution camera and other sensors can fly for perhaps 40 to 50 minutes. This flight time is enough to inspect cell towers for damage, or roofs for leaks. It also allows enough time to efficiently map a field to gauge crop growth and thereby decide where to fertilize, treat for pests or disease, or apply other measures.

Drones with hydrogen fuel cell systems can stay airborne longer and so capture images for a more extended time than conventional battery-powered drones. Courtesy of Doosan Mobility Innovation.

Current drones, however, still lack the endurance for certain tasks. Following a pipeline to look for leaks, for example, may require that a drone be airborne for many hours. The industry is working on ways to lengthen flight time. One is to explore new power sources. Doosan Mobility Innovation, a subsidiary of Seoul, Korea-based Doosan Corp., offers an example of this approach. The company has developed a hydrogen fuel cell-powered drone that extends operational time significantly.

“With a hydrogen fuel cell drone, two hours of flight time is possible since the energy density of the fuel cell system is three to four times higher than that of batteries,” said Sangwook Park, deputy general manager and leader of Americas and Oceania sales and business development at Doosan Mobility.

Areas of possible vegetation health issues and encroachment (arrow). Drone-based aerial imaging can combine image data from multiple spectral ranges with 3D point cloud lidar data to produce insights on vegetation encroaching on transportation infrastructure. Courtesy of Headwall Photonics.

In addition to extending flight times, the approach also helps get the drone quickly airborne again by simply swapping out the hydrogen cylinder. There’s no recharging of batteries, which takes time.

Doosan Mobility’s drones can carry about 10 lbs of payload and still fit within the 55-lb overall weight envelope. This payload capacity is enough for most off-the-shelf cameras that a drone may carry, Park said.

RMUS is working with Doosan Mobility to bring the hydrogen fuel cell drones to the U.S. market, according to RMUS’ Woods. While current U.S. regulations require drones to operate within the line of sight of a ground-based pilot, Doosan Mobility’s technology enables multihour flight times and longer travel distances.

Applications in flight

Even when operating with current technology and under existing regulations, the use of drones and the aerial mapping that they enable can produce a significant savings in money and time, said Ross Nakatsuji, product manager for remote sensing at Headwall Photonics. The Massachusetts-based company makes hyperspectral imaging platforms and instrumentation that capture image data in and beyond the visible range.

Nakatsuji cited the example of assessing vegetation encroaching on a rail line. The health of tree branches and the distance from those branches to the spot where a rail car passes is critically important.

The traditional solution would be to send a team out to map the vegetation and take measurements as needed. A new approach is to use a drone to capture hyperspectral images combined with 3D point cloud lidar data. A test run conducted with Germany’s Deustche Bahn railway company helps illustrate the benefits of this approach.

Aerial shots from a drone-based imager offer safer and faster cell tower inspection, versus sending a human worker up the ladder. Courtesy of Esri.

“It took five minutes to actually go up, make the flight, land, and walk away. You didn’t have to have somebody spend an hour and a half walking along this area and coming up with data that was probably not as good as we got from the drone,” Nakatsuji said.

The imaging resolution achievable with a drone is determined by the sensor’s capabilities, the optics, and knowledge of the drone’s location at the time the imaging data is captured. Standard U.S. Geological Survey maps generated by satellites or manned aircraft have several meters resolution per pixel at best. By using high-precision IMUs, drones offer at least one to two orders of magnitude improvement, making the vegetation image data they generate more detailed and useful, according to Nakatsuji.

Drones are also enabling unique solutions for inspecting infrastructure. Japan-based NTT is among several companies that have automated cellphone tower inspection using drones. As a result, a two-person job that used to take two hours can now be done by one person in 30 to 45 minutes, according to Jeremiah Johnson, an imaging solutions specialist with geographic information systems software supplier Esri.

Many of the advancements that make this possible — including lightweight imagers and robust IMUs — came out of the cellphone market, Johnson said. So it seems only fitting that drones should make maintaining the infrastructure behind these phones easier.

Johnson noted that at one time such inspections required higher-resolution cameras and high-power optics because the drone had to stand off at a distance to ensure it didn’t run into anything protruding from the tower.

With the addition of navigational cameras and other sensors providing information about the surroundings, drones have gotten better at avoiding collisions and operating in tight spaces. The payoff is the option to use simpler, lighter cameras and optics for tower inspection. As onboard computing and sensor intelligence improve, drones may soon be able to perform inspections independently of human intervention.

Filmmakers, in the industry that pioneered the use of drones for aerial imaging, now benefit from the innovations arising from these other applications. They also profit from the ingenuity of those engaged in drone aerial cinematography.

“We keep enabling creators to create shots they wouldn’t have been able to do in the past,” Freefly’s Firchau said.